1. Field of the Invention
This invention relates to an electronic security system for controlling access to electrically actuated devices and/or systems such as automotive vehicle and, more particularly, to a microprocessor controlled electronic security system for an automotive vehicle which incorporates plural contact actuatable, preprogrammed memory devices which provide authorization and/or reprogramming codes for controlling the operation of the access controlling electronic security system.
2. Description of Related Art
Security systems for automobiles and other mechanically driven vehicles have traditionally included two security features--door and ignition locking systems. The door lock limits access to the operator's compartment to those persons possessing a key mechanically configured to unlock the door lock. Similarly, the ignition lock prevents the unauthorized engagement of the vehicle's engine and drive system except by those persons possessing a key mechanically configured to disengage the ignition locking system. While such systems have enjoyed limited success in preventing unauthorized use of motor vehicles, the large number of vehicle thefts clearly show that such security systems are often inadequate.
To further secure the automobile, numerous secondary security systems, many of which have focussed on the ignition system, have been proposed. One such system is the so-called "kill" switch which is used to interrupt the electrical connection between the ignition locking system and the engine and drive system. Once installed in an automobile, turning the ignition key will not activate the engine unless the kill switch is closed. In most cases, the kill switch is carefully shielded from view, thereby making it difficult for potential thieves or other unauthorized users from closing the switch and enabling the ignition switch.
Conceptually similar to kill switches are the use of plug connectors in combination with an interruption of the electrical connection between the ignition locking system and the engine and drive system. Again, the aforementioned electrical connection is interrupted. However, rather than installing a switch capable of selectively completing the broken electrical connection, a prong-receiving socket is inserted into the break. When inserted into the socket, a corresponding prong will complete the electrical connection, again enabling the ignition switch. Like kill switches, plug and socket system are often carefully shielded from view. However, once located, plug and socket systems are superior to kill switches in that the potential thief or other unauthorized user must either somehow complete the electrical connection inside the socket or re-route the electrical connection around the socket before the ignition system will be enabled.
One deficiency common to both primary ignition key systems and secondary plug and socket security systems is the relatively small family of keys which are available. For example, while a key capable of unlocking an ignition lock has a relatively complicated shape, mechanical limitations in the shape of the lock and key systems, particularly in light of mass manufacturing needs, severely limit the number of possible shapes in which the key may be formed. As a result, a collection of 40 or so keys can unlock the majority of automobiles built by a single manufacturer. Similar problems plague the plug and socket security systems where only a limited number of complimentary plug and socket shapes are in use.